The right cylinder for the job

[SCAR_Jester]

Hi all,

Away from home with no access to accurate measures at the moment, but planning on a build that involves a 363mm x 6.02mm barrel.
I'd like to know the best cylinder to use for the job? - I should note that the piston and gears are short stroked by 2 teeth and the AoE has been corrected also, so this should be factored into the remaining volume.

I'm between a Type B or Type C cylinder (using the LayLax as a standard of types, sorry if this is incorrect terms) - or I could just use a full one?..

The RIF will be running "around" 340-360fps, I have yet to play with springs.

I would like to hit around 2:1 ratio, even though I have very good low noise and stable flight with 1.6:1 at the moment.
 
Would love recommendations of ratios to aim for also please. - is 2:1 better than 2.5:1? I hear that 3:1 and higher is really DMR/bolt action on heavy bb areas (not sure I can even get that high!).

Any help appreciated, I'm a little all over the place in my head!

Cheers

-J

 

[Iceni]

I'd always go with a full cylinder.

There's a good reason as well. It stops your sealing o-rings getting worn so fast.

Provided the gun is at a reasonable ROF (less than 25), And the piston head has reasonable ventilation you shouldn't see much difference in ported or not.

You'll struggle to hit 2.5:1 with that setup.

AOE correction is normally 3-5mm lost, 2 teeth is another 10mm. So 13-15mm of travel and volume lost before you begin.

Functional length of a standard piston is 58mm, bore 23.5 (note functional length not the length of the piston).

So without the modifications, you have made your best ratio would be 2.43:1

With them and no further modifications 1.81 to 1.89:1.

Personally, I'd already regard the system as under volumed.


The longer barrel 363 will increase your fps slightly. If you were to cut the barrel to say 300mm then the volumes would look better, but the FPS would also drop slightly. The consistency shot to shot would improve.

You see volume balancing isn't done for any other reason than shot consistency. The closer you are to 2.5:1 and the shorter the barrel (within reason) the more consistent the gun will act. This means the hop will be more consistent and the overall effect will be a more predictable gun.

3:1 is possible on an AEG.

Full rack 58mm, non AOE corrected. 295mm 6.02 = 3:1
Full rack 53mm, AOE 5mm,  270mm 6.02 = 2.99:1


It would totally depend on what you want the rifle to do IMO. If you are looking for a high ROF build then volume balancing isn't going to work out for you. If you are going for a slower ROF with more onus on single shot placement then it's one of the ways to get shot on shot placement.

The biggest problem is a lot of it is hedge wizardry. And runs hand in hand with getting a perfect setup. It's not the calculation that is doing the work, it's the commitment to detail and getting everything perfect.

I've done a few of my guns at over 2.5:1, but with that, I have spent time looking at buckings, and inner barrels, It's not just the ratio and setting up that ratio that has made those guns shoot well. I've also done the work on the gearbox and air seals to make those near to perfect.

Equally, I have guns that I've never bothered to calculate because they shoot so well. And I know for a fact the likes of my G3 are running under volumed since they run a full-length 500mm inner barrel. On the field, however, the gun works flawlessly. The air seals and bucking got corrected on the mosfet install, but no work was done to volume balance. And in all seriousness, it doesn't need that work doing to it. But in addition that gun has a significantly slower ROF than my other guns at 15rps. And I tend to use the gun single shot only as a 350fps sniper.


 

 

[SCAR_Jester]

I'd always go with a full cylinder.

There's a good reason as well. It stops your sealing o-rings getting worn so fast.

Provided the gun is at a reasonable ROF (less than 25), And the piston head has reasonable ventilation you shouldn't see much difference in ported or not.

You'll struggle to hit 2.5:1 with that setup.

AOE correction is normally 3-5mm lost, 2 teeth is another 10mm. So 13-15mm of travel and volume lost before you begin.

Functional length of a standard piston is 58mm, bore 23.5 (note functional length not the length of the piston).

So without the modifications, you have made your best ratio would be 2.43:1

With them and no further modifications 1.81 to 1.89:1.

Personally, I'd already regard the system as under volumed.


The longer barrel 363 will increase your fps slightly. If you were to cut the barrel to say 300mm then the volumes would look better, but the FPS would also drop slightly. The consistency shot to shot would improve.

You see volume balancing isn't done for any other reason than shot consistency. The closer you are to 2.5:1 and the shorter the barrel (within reason) the more consistent the gun will act. This means the hop will be more consistent and the overall effect will be a more predictable gun.

3:1 is possible on an AEG.

Full rack 58mm, non AOE corrected. 295mm 6.02 = 3:1
Full rack 53mm, AOE 5mm,  270mm 6.02 = 2.99:1


It would totally depend on what you want the rifle to do IMO. If you are looking for a high ROF build then volume balancing isn't going to work out for you. If you are going for a slower ROF with more onus on single shot placement then it's one of the ways to get shot on shot placement.

The biggest problem is a lot of it is hedge wizardry. And runs hand in hand with getting a perfect setup. It's not the calculation that is doing the work, it's the commitment to detail and getting everything perfect.

I've done a few of my guns at over 2.5:1, but with that, I have spent time looking at buckings, and inner barrels, It's not just the ratio and setting up that ratio that has made those guns shoot well. I've also done the work on the gearbox and air seals to make those near to perfect.

Equally, I have guns that I've never bothered to calculate because they shoot so well. And I know for a fact the likes of my G3 are running under volumed since they run a full-length 500mm inner barrel. On the field, however, the gun works flawlessly. The air seals and bucking got corrected on the mosfet install, but no work was done to volume balance. And in all seriousness, it doesn't need that work doing to it. But in addition that gun has a significantly slower ROF than my other guns at 15rps. And I tend to use the gun single shot only as a 350fps sniper.


 

Thanks for your advice, this really helped.

I think I might have a spare brass full cylinder somewhere which means less to buy!

My role for the RIF will be to mostly semi-auto it, a bit of CQB, and occasionally a “fair” speed on full outdoors, but I use semi all too much haha

 

[Iceni]

If that's the case I'd run the full cylinder with the 363 uncut. Leave the gears and the AOE correction in place.

Get a decent bucking in like a prommy purple, and correct every airseal. Since it's a DMR style semi most of the time build you could even run an oversized piston ring. Standard are 19x2.5x70 shore, oversized is 20x2.5 x70 shore nitrile. It's a bit of a fiddle getting the ring in place, and it will feel like it's adding a fair bit of resistance, but the seal will be epic.

If you are worried about anything I've said just ask.

O-rings are standard parts. Not airsoft parts. Get them in bulk from a bearing supplier.

https://simplybearings.co.uk/shop/Seals-O-Ring-Seals-NITRILE-O-Rings/c19_4501_4705/index.html


 

Standard is 19mm ID x 2.5mm x 70 shore.
Oversized 20mm ID x 2.5mm x 70 shore.


If you order 50 there about £6 a set. So about 12p each. The extras sell to your mates for £1 each lol. And tell them there special oversized ones.. They will have no idea and you'll get your money back off the first idiot who buys 10 for £5.


 

 

[SCAR_Jester]

If that's the case I'd run the full cylinder with the 363 uncut. Leave the gears and the AOE correction in place.

Get a decent bucking in like a prommy purple, and correct every airseal. Since it's a DMR style semi most of the time build you could even run an oversized piston ring. Standard are 19x2.5x70 shore, oversized is 20x2.5 x70 shore nitrile. It's a bit of a fiddle getting the ring in place, and it will feel like it's adding a fair bit of resistance, but the seal will be epic.

If you are worried about anything I've said just ask.

O-rings are standard parts. Not airsoft parts. Get them in bulk from a bearing supplier.

https://simplybearings.co.uk/shop/Seals-O-Ring-Seals-NITRILE-O-Rings/c19_4501_4705/index.html


 

Standard is 19mm ID x 2.5mm x 70 shore.
Oversized 20mm ID x 2.5mm x 70 shore.


If you order 50 there about £6 a set. So about 12p each. The extras sell to your mates for £1 each lol. And tell them there special oversized ones.. They will have no idea and you'll get your money back off the first idiot who buys 10 for £5.


 

That sounds good, however I might stray clear of the o-ring since I won't be going much higher than 360fps, and will occasionally be putting in a 300mm x 6.08mm barrel for CQB fps limits, and since I run a very snappy system I don't want to test it by adding resistance to the piston and possibly cause PME when I switch the battery up!

However, that link will be favourited, cheers!!

 

[Iceni]

The fps doesn't matter so much with rings but your possibly right about the PME. I've never managed to force it with an o-ring but there is always the chance you could.

I will at some point test one in a 25rps build just to see what happens. I'm expecting the system not to notice but you never know.

 

[SCAR_Jester]

The fps doesn't matter so much with rings but your possibly right about the PME. I've never managed to force it with an o-ring but there is always the chance you could.

I will at some point test one in a 25rps build just to see what happens. I'm expecting the system not to notice but you never know.

Without SS I I would think depending on what spring you use 25rps "could" be pushing the edge a tad. Good luck if you do haha, put a vid up and run it till it die "for science" haha

 

[Iceni]

Without SS I I would think depending on what spring you use 25rps "could" be pushing the edge a tad. Good luck if you do haha, put a vid up and run it till it die "for science" haha

Lol, I run 23rps on one gun with no gearbox modifications at all.

18:1 gears, 35k motor, 7.4v lipo, silent head system for AOE correction. 320fps.

Full cylinder, All teeth. And a 2 tooth delayer.

It double shoots on semi auto until you've discharged the battery with a few mags. I can correct it with AB on the mosfet, but I never switch it on. After a couple of mags it settles to single shot correctly at about 21-22 rps.

It's my go-to gun for skirmishing, and takes an absolute pounding. Never misses a beat and it's probably my least opened gearbox... It is a V3 gearbox tho and that might be why it has so few problems Since the motor ect are all bolted to the gearbox.